1. Field of the Invention
This invention relates to methods for preparing good hard butters from palm oil, which may be used as a replacement for cacao butter to a large extent in confectionary products such as chocolates, chocolate-flavored coatings and the like, without the occurrence of blooming even when the product is used without tempering.
2. The Prior Art
Hard butters are very important in the chocolate-making industry as a substitute for cacao butter, because while it is solid at room temperature, it melts evenly at body temperature, i.e., around 37.degree. C. Heretofore, most hard butters have been made from natural fats having fatty acid compositions and orientation similar to those of cacao butter, such as shea butter or phulwara butter. However, these vegetable butters are relatively expensive because of the comparatively poor yields from the raw starting materials which grow wild and are not widely cultivated. Moreover, the starting materials for these vegetable butters are difficult to obtain because of unstable weather and political conditions in the countries to which they are indigenous. As a result, there has been an increasing demand for cheaper and more abundant substitutes for cacao butter other than the known vegetable butters noted above.
Palm oil, which is obtained from the fruit of the palmaean plant, Elaeis guineensis Jacq., is one of the most abundant and cheap vegetable oils, because the plant is now being increasingly cultivated in Malaysia and Indonesia. In the past, it has been known to obtain hard butters from palm oil by fractionating the palm oil with a suitable solvent such as acetone, methyl ethylketone or hexane, or by collecting the mid-fraction of a hardened palm oil by solvent fractionation. Of these two known processes, the former is unacceptable because the yield of desired product is much too low when the fractionation is effected with sufficient precision so as to obtain a suitable product. On the other hand, if the fractionation is not carried out precisely enough, a large amount of high-melting glycerides in the oil unavoidably becomes mingled with the final product. When such a crude product is used in confectionaries, the undesirable phenomenon known as "blooming" occurs. The second of these two known processes is also unacceptable, because if the palm oil is preliminarily hydrogenated according to conventional techniques (with a nickel catalyst) and then subjected to a conventional solvent fractionation, it will form, as a by-product, so large an amount of the high-melting glycerides (which must be removed), that it becomes an uneconomical process for industrial purposes. Likewise, the hydrogenation of a highly unsaturated oil, such as cotton seed oil or soybean oil using an ordinary nickel catalyst will also give unsatisfactory results because of the high-melting glycerides which are inevitably by-produced in such process.
On the other hand, it has also been known that hard butters having a high trans-isomer content rarely cause blooming and thus may be used as a replacement for cacao butter. However, since the ordinary nickel catalyst is so low in the ability to isomerize the product, an oil having a high iodine value which is far different from palm oil must be used as the raw starting material, and even under special conditions, that is, under so-called "selective conditions" (i.e., low hydrogenation pressure and high catalyst concentration), it is impossible to avoid the by-production of the high melting-glycerides. In addition, other processes for bringing about the trans-isomerization of an oil or fat are also known, which processes, however, do not seem practical because deterioration of the treated oil occurs due to the isomerization catalysts generally used, such as selenium.
In order to avoid the disadvantages of the above-described prior art processes, there was developed a process which is described in U.S. Pat. No. 3,856,831 (owned by the unrecorded assignee hereof). Said U.S. patent describes a method for obtaining good hard butters by hydrogenating a fat or oil including palm oil having an iodine value within the range of 60 to 78 with the total content of linoleic and linolenic acids being less than 17 weight percent with a nickel catalyst poisoned with sulfur (6 to 21 parts of sulfur per 100 parts by weight of nickel). However, it should be noted that although this process was satisfactory for the most part at the time, there still remained some unresolved problems, in particular, in controlling the degree of catalyst poisoning. For different applications or uses, it is desirable to prepare different kinds of poisoned catalysts, that is, catalysts which are poisoned to different degrees. However, since the catalyst poisoning according to the process of U.S. Pat. No. 3,856,831 is effected by subjecting an active nickel metal catalyst to the action of a toxic gaseous sulfur compound (such as H.sub.2 S), it is practically impossible to effectively control the degree of poisoning using that process. The present invention provides improved processes for making hard butters, which overcomes the disadvantages of the prior art sulfur-poisoned catalyst processes. The present process uses a novel poisoning agent, namely methionine, as a result of which the above difficulties in controlling the degree of catalyst poisoning are completely avoided. Moreover, by using the present process, the danger inherent in using H.sub.2 S as a catalyst poison is avoided. Finally, by using the present process, there is no danger of having a food product contaminated with H.sub.2 S.
In addition to the foregoing, the following patents are noted as being relevant prior art: U.S. Pat. Nos. 3,687,989; 2,972,541; 2,942,984; 2,468,799; British Pat. Nos. 1,219,245; 861,016; 859,769; Japanese patent publication No. 135,103/75.
In view of the above-noted problems and disadvantages which characterize the prior art processes, it is an object of this invention to provide processes for making hard butters from an inexpensive raw material without the need for a tempering step, which hard butters have remarkable resistance against fat blooming and which also have good melting properties that make the product especially useful as a cacao butter substitute.
Another object of the present invention is to provide processes for hydrogenating palm oil wherein the hydrogenation reaction is easily controllable whereby to prevent over-absorption of the hydrogen.
A further object of the invention is to provide means for poisoning the catalyst used in hydrogenating the palm oil in a manner that is safe, both for operators employed during the processing as well as the ultimate consumers of the products having the hard butters incorporated therein.